The endoplasmic reticulum is a labyrinth of spaces connected together encaged by a membrane (Alberts et. al, 2010). It is where most cell membrane constituents are made and transported through (Alberts et. all, 2010). There are two different types of endoplasmic reticulum; the smooth ER and the rough ER. The smooth endoplasmic reticulum is plentiful in membrane bound enzymes (Koolman & Rohm, 2005). These enzymes catalyze incomplete reactions in lipid digestion and biotransformation (the chemical alteration of a substance within the body) (Koolman & Rohm, 2005).
The smooth endoplasmic reticulum are the sections that have no ribosomes attached (Koolman & Rohm, 2005). The smooth ER can be found in both plant and animal cells with their functions varying depending on the type of cell (Robinson, 2006). The endoplasmic reticulum has a crucial role in the biotransformation of the inward hydrophobic metabolites and xenobiotics in the liver (Song et. al, 2009). Due to the difficulty in isolating pure ER, research involving the endoplasmic reticulum has gone forward at a slower rate (Song et. l, 2009). Knoblach, a scientist, analyzed the proteome of ER lumen in mice and found two previously undiscovered proteins (Song et. al, 2009). Another scientist, Bergeron, distinguished the proteomes of rough and smooth ER and established numerous different proteins including 234 unknown proteins (Song et. al, 2009). Male mice were famished for sixteen hours and then had their livers removed (Song et. al, 2009).
The livers were removed quickly after the decapitation of the mice and then submerged in cold PBS, washed, cut, blotted, weighed, and finally cut up into tiny pieces (Song et. al, 2009). The proteins were then extracted and put through various programs to identify peptides (Song et. al, 2009). Many new proteins were discovered in the liver cells, however the functions of these proteins are still relatively unknown (Song et. al, 2009). The endoplasmic reticulum is also involved in diffusion and membrane transport due to the fact that it provides a vast surface area (Gupta, 2009).
The smooth ER is responsible for packaging proteins that need to be transported around the cell, the membrane synthesis of phospholipids, glycogenolysis (breaking down of glycogen into glucose), and drug detoxification (Gupta, 2009). In plant cells, the smooth endoplasmic reticulum transport materials throughout the cell (Robinson, 2006). There are also enzymes that can produce and digest lipids as well as membrane proteins (Robinson, 2006).
Also, the smooth endoplasmic reticulum is able to separate itself from the rough endoplasmic reticulum so that it can move newly created proteins and lipids to the Golgi body and other membranes (Robinson, 2006). In animal cells, the smooth endoplasmic reticulum is responsible for the metabolism of carbohydrates, regulating the amount of calcium ions, the synthesis and metabolism of steroids and lipids, and drug detoxification (Robinson, 2006). Within muscle cells, the smooth endoplasmic reticulum stores calcium and releases it when muscles contract (Robinson, 2006).